Dental caries is a disease characterised by dissolution of the mineral portion of the tooth. As caries progresses, destruction of tooth enamel and dentine occurs followed by inflammation of pulp and periapical tissues.
The mutans streptococci (MS) are a cluster of acidogenic, dental plaque-inhabiting streptococcal species that are considered the principal causative agents of caries. Presently, seven different MS species (known as S. mutans, S. rattus, S. cricetus, S. sobrinus, S. ferns, S. macacae, and S. downei) are recognised. Of these seven species it is mainly S. mutans and S. sobrinus that are of significance in terms of human caries.
Over the years various methods have been developed and tried with varying results, to prevent or at least alleviate the problem of dental caries. Treatments with antibiotics such as penicillin have been suggested and are effective but indiscriminately destroy both useful and harmful bacteria in the mouth leading to microbial imbalances.
In order to minimise disruption to the mouth microflora, antibiotic producing organisms have been investigated for their ability to inhibit caries. A group of organisms identified as having potential in this regard are microorganisms producing bacteriocin-like inhibitory substances (BLIS). BLIS producers of the genera Streptococcus, Staphylococcus and Enterococcus have been screened for potential application to prevention of dental caries (Balakrishnan, M. et al., Caries Res. 2001; 35:75–80).
What is sought is a non-virulent analog of the disease-causing S. mutans, or a so called effector strain. To serve as an effector strain in replacement therapy in bacterial infection, the microorganism must be non-virulent itself and able to compete successfully with the pathogenic microorganism either via competitive action and/or antibiotic action. S. mutans effector strains have been identified (Hillman et al, J Dent Res. 1987; 66:109–24; James and Tagg, N Z Dent J. 1991; 87:80–3) and show strong anti-S. mutans activity. A disadvantage with the use of S. mutans effector strains is the cariogenic potential of these strains.
S. salivarius is an alternative streptococcus species which avoids this disadvantage. In WO 01/27143 S. salivarius strains are identified which have utility in the treatment of dental caries caused at least in part by S. sobrinus. No activity was recorded against MS generally or S. mutans in particular. Similarly, in Balakrishnan (supra), S. salivarius K3 is identified as active against S. sobrinus when grown on trypticase soy broth yeast extract calcium carbonate agar medium, but had no effect on S. mutans. S. salivarius TOVE-R (Tanzer, J. M. et al.; Infect Immun., 1985, 48:44–50) is an antagonist strain and which brought about a reduction in dental caries. There have been no reports of BLIS production by this strain.
The applicants have now identified BLIS producing S. salivarius strains with a broad spectrum of activity against MS dental caries causing organisms including S. mutans. 
The present invention is broadly directed to these novel S. salivarius strains, and the use of anti-MS S. salivarius strains in the treatment of dental caries, or at least provides the public with a useful choice.